Affiliation:
1. Department of Microbiology, University of Minnesota Medical School, Minneapolis, Minnesota 55455-0312
Abstract
ABSTRACT
Previous studies established the critical roles of AlcR and alcaligin inducer in positive regulation of alcaligin siderophore biosynthesis and transport genes in
Bordetella pertussis
and
Bordetella bronchiseptica
. Transcriptional analyses using plasmid-borne
alcR
genes of
B. pertussis
UT25 and
B. bronchiseptica
B013N to complement the
alcR
defect of
B. bronchiseptica
strain BRM13 (Δ
alcR1 alcA
::mini-Tn
5 lacZ1
) revealed interspecies differences in AlcR inducer requirements for activation of
alcABCDER
operon transcription. Whereas the
B. pertussis
UT25 AlcR protein retained strong inducer dependence when produced from multicopy plasmids,
B. bronchiseptica
B013N
alcR
partially suppressed the alcaligin requirement for transcriptional activation. Functional analysis of AlcR chimeras produced by interspecies domain swapping and interspecies reciprocal site-specific mutagenesis determined that the phenotypic difference in AlcR inducer dependence was due to a single amino acid difference within the proposed inducer-binding and multimerization domain of AlcR. Structural predictions guided the design of a mutant AlcR protein with a single amino acid substitution at this critical position, AlcR(S103T), that was fully constitutive not only when produced from multicopy plasmids but also at a single-copy gene dosage. These results indicate that AlcR residue 103 affects a critical determinant of alcaligin inducer dependence of AlcR-mediated transcriptional activation. The
alcR
(S103T) mutant allele is the first
alcR
(Con) mutant allele identified.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
10 articles.
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